Volume control



1934- J. H. HAMMOND,-JR I 1,969,883

VOLUME CONTROL Filed Sept. '7, 1929 2 Sheets-Sheet 1 522 If 3 g 27 E 24I l "v1 E21 I Z8 mmmx - Y INVENTOR- JOHN mws 'HAMMOND JR.

ATTORNEY 1934- J. H. HAMMOND, JR 1,969,883

VOLUME CONTROL Filed Sept. 7, 1929 2 Sheets-Sheet 2 flz flfi 2 II IINVENTOR JOHN HAYS HAMMOND JR.

ATTORNEY Patented Aug. 14, 1934 PATENT OFFICE VOLUME CONTROL John HaysHammond, Jr Gloucester Mass. Application September 7, 1929, Serial No.390,879 I '5 Claims. (Cl. 250-20) 9 The object of this invention is toprovide an improved method of controlling the magnitude of the output ofa detector, repeater, or amplifier.

Another object or" this invention is to provide a circuit by which radiosignals, whichare weak as received, due to fading, will produce outputcurrents nearly as strong as the signals produced by the strong radiosignals and thus tend toeliminate the effects of fading. V

A further object of this invention is to provide for the automaticadjustment of a receiver circuit so that it may operate at maximumsensitivity for weak stations and reduced sensitivity for strongstations, thereby preventing over-loading of the receiving and loudspeaking equipment when receiving the latter stations.

A still further object of this invention is to provide a circuit whichwill bring in each station with approximately uniform intensity asthereceiver is tuned throughout the broadcast band,

regardless of the intensity of the actual radio-v signals received.

An additional object is to provide an amplifier for use in cuttingphonograph records whereby the overloading of the last stages, whichwould cause blasting of the record, may be prevented.

These and further objects will become apparent from the followingspecification taken in connection with the accompanying drawings.

In accomplishing my invention, Iuse the currents in one part of thereceiver circuit to de-' termine the operating conditions in anotherpart of the circuit. This general idea is subject to many variations.use the currents from some part of the circuits to determine or alterthe bias of amplifier tubes. Another method, for example includes theoperation of the current in one part of the circuit to influence thedetecting properties of a detector Still another method is;to utilizethe device. currents in one part of a circuit to control the platepotential on the amplifier tubes. Y

Having thus briefiy described my invention, at-- Fig. 3 is a circuitwherein the radio frequency component existing in the output of thedetector is used to controlthe plate potential of an arm plifier device.

One method, for instance, is to,

denser 6, and the inductance '7. The grid circuit is provided with theusual grid leak 9 and grid leakcondenser 10 and the output of thedetector device includes the tickler coil 11 variably disposed relativeto the inductance 7, the output inductance 12 and the high potentialsource 13. Also included as a shunt circuit in the output ofsaiddetector device is the radio frequency bypass condenser 14, and theresistor 15, the latter of which acts as a coupling resistor and servesto, impress a potential on the grid of the volume control tube 2. Theprimary 12 of the transformer 23 is inductively related to the secondary22 which latter is included in the input circuit of the amplifier device3. The input circuit of said amplifier device includes also the couplingresistor 24, and the condenser 25. .The output of the volume controltube 2 comprises the high potential source 21 and the grid leak 24 ofthe amplifier device 3. The amplifier device 3 has, in its outputcircuit, the telephones 27 or any other reproducing device and the highpotential source 28. Referring now more particularly to Fig. 2, there isshown a similar circuit including a regenerative I detector 1, a volumecontrol tube 2, and'amplifier tube 3. The output circuit of the detectordevice 1 includes the radio by-pass condenser 14, in series with theinductance 12 and across the said con denser there is disposed theinductance 17 which constitutes the primary of the transformer 19, thesecondary of which is adapted to supply the Volume control tube 2. Inother respects, this circuit is similar to that of Fig. 1, similar partsbeing designated by the same reference numer-. als. I Referring now moreparticularly to Fig. 3,-there is shown a circuit which utilizes thevolume control tube to vary theplate potential of the amplifier device.This circuit comprises the regenerative detector circuit including. thedetector 1 which circuit is similar to that shown in Figs. 1 and 2. Thevolume control tube 2 is adapted to be supplied by means of the resistor15 included in the radio frequency by-pass circuit ineluding alsotheradio frequency by pass condenser 14, in a similar manner tothat inwhich the volume control tube 2 is supplied in Fig. 1. The output of theregenerative detector is through the primary 12 of the transformer 23the secondary 22 of which is adapted to supply the amplifier device 13inthe usual manner. A by-pass condenser may be provided across the winding12 as shown. The plate circuit of the amplifier device 3 includes thedutputjinductance 27, the resistor 26, and the high'potential source28'. The resistor 26 is included also in the plate circuit of the volumecontrol tube 2 in which circuit, but

The transformer 30, the primary 2'7 of which is in the output circuit ofthe ampiifier device 3, is

' There isprovided a radio frequency by-pass circuit including theby-pas's condenser 14 and the resistor 15 which latter is adapted tosupply a potential to the grid of the volume control tube 2 through the'gridle'ak 20" and grid leak condenser 16. The output circuit of thevolume control device 2 includes the grid leak 9 of the detector device1', and the plate potential of said device is-supplied by source 13.--The secondary 22 of the transformer 23 isadap'ted to supply thesucceeding amplifier stages-in the usual and Well known manner. I I

Having thus described the circuits embodying my invention I will nowdescribe their operation. In the case of the circuit shown in Fig. 1',the radio frequency current existing in and bypassed by the platecircuit of the detector 1 is impressed upon the grid circuit of thevolume control tube 2, and the plate circuit of the volume control tube2 includes the resistor 24, the latter of which is shunted by thecondenser 25 as shown. The

direct current in the plate circuit of 'the'volume control tube2'flowing'through the resistor 01 grid leak 24 is made to depend uponthe amount of voltage impressedacross the resistor 15 in a well knownmanner. The resistor 24 isincor orated in the grid circuit of theamplifier tube 3.

Adjustments are suitably made, such that onw'eak signalsthe bias onS issuch asto give maximum amplification. As the signals increase, theamount of radio frequency current by-pas's'ed'from the plate ofthedetector tube increases, thereby in: creasing the direct platecurrent'of tube 2,;a'nd consequently increasing the bias of tube 3. Thisproduces a condition of operationof tube 3, givingless amplificationsothat strong signals from the transformer 23 do not produce relatively sogreat amplification as do the weak signals" passing therethrough. V I vIt is to be noted that in this case the input of the volume control tube2 is radio frequency, while fit the current controlling the bias ofamplifier tube 2 is of lower frequency than the audio currents,-

corr'esponding to a D. C. bias changing only the variation inthe amountof radio signal strength at the rate of fading.-- Thus the true audiotones are insertedinto the grid circuit of amplifier tube 3 bytransformer 22, and frequencies inserted by the bias resistor 24 are ofa lower order of magnitude, such that the output circuit of theamplifier will not respond to their presence.

In Fig. 2 the strength of the audio current in the plate circuit of thedetector tube is made to control the bias in the grid circuit of theamplifier tube, as the radio frequency existing in the output circuit ofthe detector 1 is by-passed by the condenser 14 and is therefore notimpressed upon the input of the volume control tube 2. The rectifiedoutput of the'volume control tube 2, however,

serves to vary the bias of the amplifier device 3 in the same manner asin Fig. 1.

In the broadcasting art, it is often the intent that'the'r'e shall bechanges in the volume of the signals. and this is accomplished bychanging the amount of modulation. In order to have auto- .matic-controlof volume which will operate from changes of the radio carrierintensity, but not from changes in the radio carrier modulation, it isdesirable to provide the control stimulus from circuits carrying energyrepresentative of the radio frequency,- as is shown in Fig. 1. In asuperheterodyrie, the stimulus may be applied or supplied by theintermediate circuit, or the plate circuit of the second detector.-stimulus is supplied by the audio'frequency as shown in Fig. 2, theautomatic control will not be able to discriminate between theintentional changes, that is, change in volume of transmission, and tochanges which it is desired to correct; and therefore in general Fig.2would usually not be preferable. In either of the forms shown in Figs. 1and 2, the control tube may be used to con trol the bias on a number 'ofamplifier circuits as, for example, in the super'heterodynait maybe usedto control the bias of a large number of tubes producing considerablygreater effect.

In Fig. 3 the circuit is arranged to' control the amplification byvariation of the plate voltage of the amplifier tubes. This is similarto Fig. 1, except that the tube 2 controls the applied plate voltage ofthe amplifier tube 3. For this purpose the tube 2 has in its input theresistor 15 in the In Fig. 4 the'control tube is adapted to varythe- Ifthe controlling 1 detector characteristics of the detector 1. In

this circuit the detector bias which'is produced by the plate current ofthe volume control tube 2 flowing through the resistor'9', is variedin-accordance with the radio frequency existing in the out-- put of thedetector 1, which is applied to the input of the volume control tube 2.This detector employs so-called plate rectification, and is biasednormally to such a value that the increasing radio signals increase thedirect current in its plate circuit. The volume control tube 2 isconnected through the grid leak 20, and condenser '11 for radioexcitation from the radiofrequency by-pass' circuit of the detector. 1.This tube employs grid rent'of this tube. As a result the'currentthrough the resistor 9 is diminished and the bias'is dimin ished to apoint where the detector acts as an amplifier with little or nodetection.

The circuits embodying my invention have equal utility in the control ofthe current for use in the cutting of phonograph records wherein it isnecessary to limit the amplitude of the cut to prevent blasting. Theamplifier for the cutter may be arranged to have its last stagescontrolled in accordance with this invention, and thereby prevent theundesirable distortion in the record produced.

Having thus described my invention, it is to be understood that I'amnot-to be limited to the specific embodiment shown and described for thepurpose of illustration only, but by the scope of my invention as setforth in the appended claims.

I claim:

1. In a receiving system, a detector having an input and an outputcircuit, an amplifier coupled to the detector output and a source ofsignal modulated carrier energy coupled to said input, said detectoracting upon said modulated carrier energy so that there exists in thedetector output circuit separable high frequency and low frequencycomponents of the signal modulated carrier energy, means for segregatingand transforming said high frequency component into a direct current ofan intensity varying in accordance with the intensity of the highfrequency component and means for impressing said direct current upon aportion of said amplifier for controlling the amplification thereof inaccordance with the intensity of the direct current.

2. In a receiving system a detector device comprising an input circuitcoupled to a source of signal modulated carrier energy and an outputcircuit coupled to a vacuum tube amplifier, said detector device actingto render separable the carrier energy and the signal energy componentsof said signal modulated carrier energy, means for segregating andtransforming a portion of one of said components into direct current ofrelated intensity and means to control the static potential of the anodeof said vacuum tube amplifier in accordance with the amplitude of thedirect current.

3. In a signalling system, a detector device comprising an input circuitcoupled to a source of signal modulated carrier energy and an outputcircuit coupled to an amplifier system including at least one vacuumtube amplifier, said detector acting to render separable the carrierenergy and the signal energy components of said signal modulated carrierenergy, means for segregating and transforming a portion or" saidcarrier energy component into direct current of related intensity andmeans to control the static potential of the anode of .said vacuum tubeamplifier in accordance with the amplitude of the direct current.

4. In amplifying systems and the like, a detector relay comprising anelectronic tube provided with an input circuit and an output circuit, asource of signal modulated carrier energy coupled to said input circuit,an amplifier relay having input and output circuits, means for couplingthe detector relay output circuit to the amplifier relay input circuit,a carrier energy by-pass path forming a part of said detector relayoutput circuit, means for controlling the amplification characteristicsof said amplifier relay comprising an electronic tube having an inputcircuit including at least a portion of said 100 carrier energy by-passpath and an output circuit including a source of current parallellydisposed with respect to the amplifier relay output circuit.

5. In amplifying systems or the like, a detector 105 relay provided withinput and output circuits, an amplifier coupled to the detector outputcircuit and a source of signal modulated carrier energy coupled to thedetector input circuit, said detector relay acting upon the modulatedcar- 110 rier energy so that there exists in the detector relay outputcircuit separable carrier energy and signal energy components of thesignal modulated carrier energy, means for segregating and transformingthe carrier energy component into 11 V a direct current of an intensityvarying in accordance with the intensity of the carrier energy componentand means for impressing the direct current into a portion of saidamplifier for controlling the amplification thereof in accordance withthe intensity of the direct current.

JOHN HAYS HAMMOND, JR.

